If you're not using Tailwind for your CSS needs - I highly recommend it. It's now a staple of my product building toolkit, and it just fits so well with Vue.js and Nuxt workflows that I can't imagine moving to something else.

One thing about Tailwind is it leaves the Javascript to you. This is so it's library-agnostic.

For most of my projects I want that smooth shadow under the navbar - here's the code I use to achieve it.

The effect we're going for

The HTML

<nav 
    :class="{ 'scrolled': !view.atTopOfPage }" 
    class="fixed flex w-full bg-white border-b items-center justify-between flex-wrap p-5 m-auto top-0 animated">
</nav>

Here, we're adding the .scrolled class when the value in view.atTopOfPage is false.

The CSS


nav {
    z-index: 10
}

nav.scrolled {
    @apply shadow-2xl;
    border-bottom: 0px;
}

Apply the shadow to the navbar when it has the class scrolled.

The Javascript

I have a navbar component that I use throughout the app, so this code would go there.

// in data, I like to store a view object with all 
// the values I need for a component to manage 
// it's 'view' state - ie loading, 
// or in this case, if the user is at the top of the page or not
data () {
    return {
        view: {
            atTopOfPage: true
        }
    }
},

// a beforeMount call to add a listener to the window
beforeMount () {
    window.addEventListener('scroll', this.handleScroll);
},

methods: {
	// the function to call when the user scrolls, added as a method
    handleScroll(){
        // when the user scrolls, check the pageYOffset
        if(window.pageYOffset>0){
            // user is scrolled
            if(this.view.atTopOfPage) this.view.atTopOfPage = false
        }else{
            // user is at top of page
            if(!this.view.atTopOfPage) this.view.atTopOfPage = true
        }
    }
}

The Result

Buttery smooth shadows on your navbar. Check it out in action on my product Referextra.com